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Quiver varieties and Weyl group actions. (English) Zbl 0958.20036
For a finite graph of type $$ADE$$ with set of vertices $$I$$, H. Nakajima associated to $$\mathbf{v,w}\in\mathbb{N}^I$$ a “quiver variety” $$\mathcal M(\mathbf{v,w})$$ and constructed a Weyl group action on the cohomology of $$\sqcup_{\mathbf v}\mathcal M(\mathbf{v,w})$$ using techniques of hyper-Kähler geometry [see Duke Math. J. 76, No. 2, 365-416 (1994; Zbl 0826.17026), Duke J. Math. 91, No. 3, 515-560 (1998)]. In the paper under review it is given an alternative construction of this Weyl group action, based not on hyper-Kähler geometry, but on techniques of intersection cohomology. This gives in fact a refinement of the Weyl group action.

##### MSC:
 20G10 Cohomology theory for linear algebraic groups 20G05 Representation theory for linear algebraic groups 14L30 Group actions on varieties or schemes (quotients)
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##### References:
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